JPH0548187A - Polarizing laser - Google Patents

Abstract

(57) [Abstract] [Purpose] Achieving a stable laser output, eliminating the need for complicated design on the device side that uses laser light, and eliminating the directionality during processing. Provided is a polarized laser device. An output control depolarization unit 13 having an attenuator and a depolarization element for attenuating the laser output light 8 by utilizing polarization characteristics is provided on the optical axis of the laser output light 8 outside the laser resonator. As the attenuator, a pair of two quartz plates which are tilted in opposite directions about the axis perpendicular to the laser output optical axis and which rotate in the opposite direction and at the same angle are used. The laser output light 8 is monitored by the output monitor 9, and the controller 11
By controlling the rotation of the quartz plate, the output is controlled without changing the operating conditions in the laser resonator. The laser output light 8 transmitted through the quartz plate is depolarized by the depolarizing element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarized laser device used as a light source for exposure for fine processing of semiconductor integrated circuits.

[0002]

2. Description of the Related Art In recent years, excimer lasers have attracted attention as a high-efficiency, high-power laser in the ultraviolet region among lasers. The excimer laser is particularly expected as a light source for exposing a fine pattern of a semiconductor integrated circuit. The excimer laser uses a combination of a rare gas such as krypton or xenon as a laser medium and a halogen gas such as fluorine or chlorine to generate an oscillation line having a sufficient output for pattern exposure at some wavelengths between 353 nm and 193 nm. Obtainable. However, if the laser light is polarized,
The shape and accuracy of the pattern may differ depending on the processing direction of the pattern.

Generally, in order to control the output of a laser, a method of changing the excitation intensity for exciting the laser medium or adjusting an optical element in the resonator is adopted.

As a conventional example, the configuration described in Japanese Patent Laid-Open No. 63-9187 will be described with reference to the schematic configuration diagram shown in FIG. The laser in this conventional example is a discharge excitation type excimer laser, and the output intensity is changed by changing the output voltage of the power source to adjust the output.

In FIG. 3, reference numeral 1 is a total reflection mirror forming a laser resonator, and 2 is a semi-transmission mirror forming a laser resonator. A laser medium 3 is provided in the optical path of the resonator. A charge / discharge excitation circuit 4 excites the laser medium 3. 5 is a high-voltage power supply that supplies power to the charge / discharge excitation circuit 4,
An optical element etalon 6 narrows the spectrum of the laser oscillated by the laser resonator. A monitor optical system 7 branches a part of the laser output light 8 oscillated from the laser resonator. Reference numeral 9 is an output monitor, which is a monitor optical system 7.
A part of the laser output light 8 branched by is monitored and a monitor signal 10 is output. Reference numeral 11 denotes a controller, which generates a feedback signal 12 for controlling the voltage of the high-voltage power supply 5 according to the monitor signal 10.

The operation of the laser device configured as described above will be described below.

A monitor optical system 7 monitors a part of a laser output light 8 oscillated from a laser resonator composed of a total reflection mirror 1 and a semi-transmission mirror 2 and narrowed in band by an optical element etalon 6 by an monitor optical system 7. To introduce. The controller 11 outputs the feedback signal 12 according to the monitor signal 10 output from the output monitor 9 to control the voltage of the high-voltage power supply 5. By changing the voltage of the high-voltage power supply 5 by the feedback signal 12, the excitation intensity for exciting the laser medium 3 can be changed, and accordingly, the amplification factor amplified when the laser light passes through the laser medium 3 changes. Therefore, the laser output can be controlled.

[0008]

However, in the configuration of the above-mentioned conventional example, when the excitation intensity for exciting the laser medium in the laser resonator is rapidly changed and the optical element is adjusted, this optical Since the operating conditions of the element are changed drastically, the thermal load on the laser medium and the optical element changes, and the abundance ratio of atoms and molecules in the steady state of the laser medium changes. The operating conditions in the laser resonator, such as generation or adsorption of impurity gas, change. As a result, it is difficult to stabilize the laser output. Also, when applying polarized light to laser processing, design an optical system that takes into consideration the optical characteristics such as the difference in the processing cross section depending on the processing direction and the difference in the reflectance of S-polarized light and P-polarized light. There was a difficulty that I had to do.

The present invention solves the above-mentioned problems of the prior art. It is possible to obtain a stable laser output by controlling the laser output without changing the conditions in the laser resonator. , The device side that uses laser light does not require a complicated design considering the polarization direction,
Moreover, it is an object of the present invention to provide a polarized laser device in which the directionality at the time of processing is eliminated so as not to cause a disadvantage to the device side that uses laser light.

[0010]

To achieve this object, the present invention provides a laser resonator, monitor means for monitoring laser output light oscillated from the laser resonator, and laser output outside the laser resonator. Two pairs are provided on the optical axis and are inclined in opposite directions, and are rotated in opposite directions and at the same angle with respect to parallel vertical lines intersecting with the laser output optical axis, respectively. An attenuator comprising an even number of quartz plates for attenuating the laser light, a depolarizer provided on the laser output optical axis on the side opposite to the laser resonator, and the monitor means And a control means for controlling the output by rotating the attenuator in accordance with the monitor signal from.

[0011]

According to the present invention, according to the above construction, the laser output light oscillated from the laser resonator is monitored by the monitor means to output a monitor signal, and the monitor signal causes the control means to incline in opposite directions. The attenuator consisting of a pair of quartz plates is rotated in the opposite direction and at the same angle by the parallel rotation axis that intersects the laser output optical axis, the laser output light is attenuated using the polarization characteristics, and then the depolarizer is used. The laser output light can be nonuniform light. Since the laser output light monitoring means, attenuator, and depolarization element (in particular, depolarization means) are all provided outside the laser resonator, it is not necessary to drastically change the operating conditions inside the laser resonator. , It becomes possible to control the output. Further, since the non-polarized laser light is output, it is possible to eliminate the trouble of making a complicated design in consideration of the polarization direction on the device side that uses the laser light, and moreover, when applying it to laser processing, Directionality can be eliminated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a polarized laser device according to an embodiment of the present invention. In FIG. 1, 1 is a total reflection mirror that constitutes a laser resonator, and 2 is a semi-transmission mirror that constitutes a laser resonator. A laser medium 3 is provided in the optical path of the resonator. A charge / discharge excitation circuit 4 excites the laser medium 3. Reference numeral 5 is a high-voltage power supply that supplies power to the charge / discharge excitation circuit 4, and 6 is an optical element etalon, which narrows the spectrum of the laser oscillated by the laser resonator. A monitor optical system 7 branches a part of the laser output light 8 oscillated from the laser resonator. An output monitor 9 monitors a part of the laser output light 8 branched by the monitor optical system 7 and outputs a monitor signal 10.
A controller 11 generates a feedback signal 12 according to the monitor signal 10. Reference numeral 13 denotes an output control depolarization unit, which is a laser output light 8 outside the laser resonator.
Of the depolarizer and an attenuator which is provided on the optical axis of and is controlled according to the feedback signal 12.

The polarization laser device configured as described above will be described in more detail below together with its operation.

A laser output light 8 oscillated from a laser resonator composed of a total reflection mirror 1 and a semi-transmission mirror 2 and band-narrowed by an optical element etalon 6 is output control depolarization unit 13.
Through the laser beam to reach the monitor optical system 7, a part of the laser output light 8 is branched and introduced into the output monitor 9. The controller 1 according to the monitor signal 10 detected by the output monitor 9
1 outputs a feedback signal 12 to control the output control depolarization unit 13. The attenuator of the output control depolarization unit 13 rotates together with the output control depolarization unit 13 or alone as a rotation axis perpendicular to the optical axis of the laser output light 8 according to the feedback signal 12 to control the resultant output. In addition, the depolarizing element makes the laser output light 8 unpolarized.

The details of the output control depolarization unit 13 will be described. FIG. 2 is a schematic perspective view showing the output control depolarization unit 13. As shown in FIG. 2, the output control depolarization unit 13 includes a pair of quartz plates 14 that are attenuators.
a and 14b, and a depolarizer 15 which is an optical element for making polarized light unpolarized. Each quartz plate 14
a and 14b are arranged in a V-shape that is symmetrically inclined in the opposite direction with respect to the optical axis of the output light 8 so that the laser output light 8 is incident at an incident angle θ, and is perpendicular to the optical axis of the laser output light 8. The rotating shafts 16a and 16b which are parallel to each other are supported so as to rotate in opposite directions and at the same angle. The depolarizer 15 is installed on the optical axis of the laser output light 8 on the opposite side of the quartz plates 14a and 14b from the laser resonator.

Generally, when the light incident on the quartz plate is polarized light, the transmittance changes according to the incident angle θ. That is, the laser output light 8 can be attenuated by changing the incident angle θ. Therefore, the laser output light 8 that oscillates
Is polarized, the quartz plates 14a and 14b are rotated in parallel with the rotation axes 16a and 16 which are orthogonal to the optical axis of the laser output light 8.
By rotating in the opposite directions by b and interlocking with the same angle, the transmittance changes with the change of the incident angle θ, so that the output can be controlled. Quartz plate 14
The laser output light 8 transmitted through a and 14b is depolarized element 1
It can be made non-polarized by 5.

The above control is all performed outside the laser resonator and has no influence on the laser oscillation condition, so that more stable output control can be performed as compared with the conventional technique. Further, by disposing the two quartz plates 14a and 14b in a V-shape that is inclined in opposite directions, the optical axis of the laser output light 8 does not shift before and after passing through the output control depolarization unit 13. is there. Furthermore, laser output light 8
After passing through the quartz plates 14a and 14b, the depolarizer 1
Since the laser output light 8 is transmitted through the laser beam 5, the laser output light 8 becomes unpolarized, and there is an advantage that the influence of the directionality of laser processing can be eliminated.

[0019]

As described above, according to the present invention, the laser output light oscillated from the laser resonator is monitored by the monitor means to output the monitor signal, and the monitor signal causes the control means to operate outside the laser resonator. The attenuator consisting of a pair of quartz plates tilted in opposite directions on the laser output optical axis is rotated in the opposite direction and at the same angle by the parallel rotation axis intersecting the laser output light, and the polarized light is used. Since the laser output light is attenuated by this, the output can be controlled without changing the operating conditions in the laser resonator. Therefore, a stable output can be obtained. In addition, the depolarization element installed on the side of the laser output optical axis opposite to the laser resonator with respect to the attenuator can make the laser output light into an inhomogeneous light. It is possible to eliminate the need for a complicated design in consideration of the above and to eliminate the processing direction. Therefore, it is possible to prevent the device side using the laser light from being disadvantageous.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a polarization laser device according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing an output control depolarization unit used in the same polarized laser device.

FIG. 3 is a schematic configuration diagram showing a conventional polarized laser device.

[Explanation of symbols]

 1 Total Reflector 2 Semi-Transparent Mirror 3 Laser Medium 4 Charge / Discharge Excitation Circuit 5 High Voltage Power Supply 7 Monitor Optical System 9 Output Monitor 11 Controller 13 Output Control Depolarization Unit 14a Quartz Plate 14b Quartz Plate 15 Depolarization Element 16a Rotation Axis 16b Rotation Axis

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoya Horiuchi 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. (72) Keiichiro Yamanaka 3-chome, Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture No. 10-1 Matsushita Giken Co., Ltd. (72) Inventor Takeo Miyata 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Matsushita Giken Co., Ltd.

Claims (1)

[Claims] 1. A laser resonator, a monitor means for monitoring laser output light oscillated from the laser resonator, and two sets of two on the laser output optical axis outside the laser resonator are tilted in opposite directions. It is composed of an even number of quartz plates which are provided in parallel, and which are rotated in the opposite directions with the parallel vertical lines intersecting with the laser output optical axis as rotation axes and at the same angle to attenuate the laser light by utilizing polarization characteristics. An attenuator, a depolarizing element provided on the optical axis of the laser output on the side opposite to the laser resonator with respect to the attenuator, and rotating the attenuator in response to a monitor signal from the monitor means to output. And a control means for controlling the polarized laser device.